Tool for machining surfaces in bores

ABSTRACT

The tool comprises a tool wheel ( 5 ) which is mounted on a holding arm ( 4 ) and has a tool-wheel parent body ( 6 ) having a machining body ( 7 ) arranged at the outer margin. In one embodiment variant, this machining body is designed as an abrasive body. A base body for accommodating the bearing arrangement is designed in one piece with the holding arm ( 4 ), which also has the supply lines ( 8 ) for the hydrodynamic bearing arrangement and the hydraulic drive. A tool-centering interface ( 11 ) permits the presetting of the tools outside the machine tool.

[0001] The invention relates to a tool for machining surfaces, in particular recesses, in bores of workpieces, having a tool wheel which is mounted in a rotatable manner on a holding arm and whose diameter exceeds the dimension of the holding arm transversely to the longitudinal direction of the same.

[0002] DE 419 416 C discloses a grinding device having a turbine drive, in which grinding device the turbine wheels lie open for driving the grinding wheel, so that the drive medium discharges freely. Furthermore, the grinding wheel projects to a considerable extent on both sides of the holding arm, so that this holding arm, which is thin relative to the grinding-wheel diameter and in addition is also of fork-shaped design, does not have the necessary rigidity which is required for accurate machining. Furthermore, the open airflow or spray against the turbine blades limits the power transmission, for which reason a turbine of relatively large diameter is used, this turbine requiring an even larger grinding wheel, so that, during the machining of surfaces in bores, there are restrictions with regard to the inside diameter of these bores.

[0003] The object of the invention is to design a tool of the specified type in such a way that, at a relatively low design cost, small external dimensions for the machining inside small bores and relatively large chip-removing capacities can be achieved.

[0004] According to the invention, this object is achieved by a tool of the type specified at the beginning in that the tool wheel consists [sic] a hollow tool-wheel parent body having an essentially rotationally symmetrical form and a machining body arranged on the outer periphery of the same, in that the tool-wheel parent body together with a base body provided on the holding arm form a housing for accommodating the bearing arrangement and the drive for the tool wheel, in that the diameter of the tool wheel exceeds the dimensions of the holding arm transversely to the longitudinal direction of the same only by slightly more than corresponds to the recess inside the bore of the workpiece, and in that the tool wheel projects beyond the holding arm only on one side of the latter.

[0005] The term “recess” refers to a groove or an internal thread.

[0006] The invention enables machining of longitudinal grooves in narrow bores, with an orientation of the grooves parallel to or at an angle to the bore axis, and the machining of thread turns, since this configuration offers compact external dimensions. Since the tool wheel is only slightly larger than corresponds to the dimension of the holding arm, the latter has high rigidity, as a result of which vibration-free machining of workpieces is possible. The interaction of the hollow rotationally symmetrical tool wheel with the base body of the holding arm creates a configuration which offers not only compact external dimensions but also protected arrangement of the bearing arrangements of the drive.

[0007] Since the tool wheel projects beyond the holding arm only on one side of the latter, especially narrow bores can be machined, since a clearance space between holder and inner bore is only required on the one side, at which the tool wheel projects beyond the holding arm.

[0008] The configuration of the tool wheel as a hollow rotationally symmetrical body provides the precondition for the machining body to be designed as an abrasive body or as a milling cutter.

[0009] An especially advantageous configuration with regard to achieving compact external dimensions is obtained if the tool-wheel parent body is of hemispherical or frustoconical design. This configuration is especially advantageous in combination with the design of the drive as a hydraulic drive, since in this way the space available can be utilized in an especially effective manner for the drive parts and also for the bearing parts.

[0010] Furthermore, it is advantageous if a projecting, bead-shaped abrasive-material support, which carries the abrasive material, is formed in one piece at the outer margin of the tool-wheel parent body, the abrasive-material support and abrasive material forming the machining body. This configuration leads in particular to a compact embodiment when, in a development of the invention, the tool-wheel parent body and the abrasive-material support are designed as a metal body, and the abrasive material is electrolytically applied to the abrasive-material support. The abrasive material may also be applied to the abrasive-material support by means of ceramic bonding, metallic bonding or synthetic resin bonding. The abrasive material may consist of cubic boron nitride or diamond. The metal body is preferably formed from steel. Such a tool provided as a grinding tool not only has compact external dimensions but also a very long service life on account of the abrasive material used.

[0011] When the grinding wheel or the milling cutter wears down, an exchange can easily be carried out on account of the configuration according to the invention, since in this case the tool-wheel parent body with the integrally formed machining body is connected as a unit to the remaining parts of the tool in an easily exchangeable manner.

[0012] A further simplification of the design is provided for by the base body being designed in one piece with the holding arm, which accommodates supply lines for the drive and/or the bearing arrangement.

[0013] If, in a further configuration of the invention, the bearing arrangement of the tool wheel is designed as a hydrodynamic bearing arrangement and the drive for the tool wheel is designed as a hydraulic drive, the oil required for the hydraulic drive may serve as lubricant for the hydrodynamic bearing arrangement of the tool wheel, a factor which reduces the design cost overall. With small dimensions, very high torques and thus high outputs can be transmitted to the tool wheel through the use of a hydraulic drive. Compared with the mechanical drives, the hydraulic drive for such a tool also has the advantage that, if the tool wheel stops suddenly, the drive cannot be damaged, as is the case in the mechanical drives on account of mass forces.

[0014] It is advantageous if the holding arm is provided with a tool-centering interface for securing to a machine tool, since the tool can be preset as a result.

[0015] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawing, in which:

[0016]FIG. 1 shows a side view of a tool with a workpiece indicated by broken lines;

[0017]FIG. 2 shows a view of the tool according to FIG. 1 rotated through 90°;

[0018]FIG. 3 shows a section through the workpiece, indicated schematically in FIG. 1, in an enlarged representation;

[0019]FIG. 4 shows a modified embodiment compared with FIGS. 1 and 2;

[0020]FIG. 5 shows a front view in the axial direction of the tool holder;

[0021]FIG. 6 shows a modified embodiment, compared with FIG. 1, of a tool wheel on an enlarged scale.

[0022] The tool shown in FIGS. 1 and 2 is designed as a grinding tool and serves in particular to machine grooves 1 inside an inner bore 2 of a workpiece 3, which is indicated by broken lines in FIG. 2 and is shown in section in an enlarged representation in FIG. 3.

[0023] As can be seen from FIGS. 1 and 2, and 4, the tool comprises a holding arm 4 and a tool wheel, which is designated overall by 5 and has a tool-wheel parent body 6. The longitudinal axis of the holding arm is designated by 4 a and, in the embodiment according to FIGS. 1 and 2, encloses a right angle with the bearing axis 5 a of the tool wheel 5, which in this case is designed as a grinding wheel. An abrasive-material support 7 is formed in one piece on the outer periphery of the tool-wheel parent body 6 and carries, for example, electrolytically applied cubic boron nitride. The abrasive-material support 7 and the applied hard particles of boron nitride form the machining body or that part of the grinding tool which is in engagement with the workpiece to be machined. The tool-wheel parent body 6 is made of metal, preferably steel, and, in the embodiment according to FIGS. 1 and 2 and in the embodiment according to FIG. 6, is designed essentially as a rotationally symmetrical, hemispherical hollow body. In the exemplary embodiment according to FIG. 4, the tool-wheel parent body is of frustoconical design and is designated by the reference numeral 10. In the case of the exemplary embodiments according to FIGS. 4 to 6, a milling cutter 9 is provided at the outer margin of the tool-wheel parent body 6 instead of the abrasive-material support 7. In the embodiment according to FIGS. 1 and 2, the abrasive-material support 7 may be replaced with a milling cutter.

[0024] The tool-wheel parent body 6 or 10 forms a housing for a drive and the bearing arrangement of the tool-wheel parent body 6 or 10 and thus of the machining body 7 or 9, this visible part of the housing, which is designated by 6 or 10, interacting with a base body which is formed by the holding arm 4. Provided inside this holding arm 4 are supply lines 8 which direct hydraulic oil to the drive motor, which is designed as a hydraulic drive motor, and in addition the bearing arrangement, which is designed as a hydrodynamic bearing arrangement, is also supplied as a result.

[0025] As can be seen from FIG. 2, the tool wheel 5, that is to say the grinding wheel 5 in the present exemplary embodiment, is arranged on the holding arm 4 in such a way that it only projects at one side edge in accordance with the radial extent of the bead-shaped abrasive-material support 7. In this way, the opposite side of the holder 4, when being inserted into the bore 2 of the workpiece 3, can virtually bear against the inner wall 2 when one of the grooves 1 is to be machined.

[0026] In the tool according to figure [sic] 4 and 5, the bearing axis (designated by 10 a) of the workpiece [sic] wheel 10 forms an acute angle with the longitudinal axis 4 a of the holding arm 4. The angular setting of the bearing axis relative to the longitudinal axis of the holding arm depends on the field of use of the respective tool. Here, too, the milling cutter may be arranged in such a way that it projects beyond the holding arm 4 only at one side edge of the latter.

[0027] Designated by 11 is a tool-centering interface, which is formed directly on a fastening flange 12 at the end of the holding arm 4. As a result, the tools can be preset, so that, after the fastening of the tool to a corresponding machine tool by means of the fastening flange 12, they already have the setting necessary for the machining. 

1. Tool for machining surfaces, in particular recesses, in bores of workpieces, having a tool wheel which is mounted in a rotatable manner on a holding arm and whose diameter exceeds the dimensions of the holding arm transversely to the longitudinal direction of the same, characterized in that the tool wheel (5) consists [sic] a hollow tool-wheel parent body (6, 10) having an essentially rotationally symmetrical form and a machining body (7, 9) arranged on the outer periphery of the same, in that the tool-wheel parent body (6, 10) together with a base body provided on the holding arm (4) form a housing for accommodating the bearing arrangement and the drive for the tool wheel (5), in that the diameter of the tool wheel (5) exceeds the dimensions of the holding arm (4) transversely to the longitudinal direction of the same only by slightly more than corresponds to the recess inside the bore of the tool [sic], and in that the tool wheel (5) projects beyond the holding arm (4) only on one side of the latter.
 2. Tool according to claim 1, characterized in that the machining body is designed as an abrasive body (7).
 3. Tool according to claim 1, characterized in that the machining body is designed as a milling cutter (9).
 4. Tool according to one of claims 1 to 3, characterized in that the tool-wheel parent body (6) is of hemispherical design.
 5. Tool according to one of claims 1 to 3, characterized in that the tool-wheel parent body (10) is of frustoconical design.
 6. Tool according to one of claims 1 or 2 or 4 or 5, characterized in that a projecting, bead-shaped abrasive-material support (7), which carries the abrasive material, is formed in one piece at the outer margin of the tool-wheel parent body (6), the abrasive-material support (7) and abrasive material forming the machining body.
 7. Tool according to claim 6, characterized in that the tool-wheel parent body (6) and the abrasive-material support (7) are designed as a metal body, and the abrasive material is electrolytically applied to the abrasive-material support.
 8. Tool according to claim 6, characterized in that the abrasive material is applied to the abrasive-material support (7) by means of ceramic bonding.
 9. Tool according to claim 6, characterized in that the abrasive material is applied to the abrasive-material support (7) by means of metallic bonding.
 10. Tool according to one of claims 6 [lacuna], characterized in that the abrasive material is applied to the abrasive-material support by means of synthetic resin bonding.
 11. Tool according to one of claims 7 to 10, characterized in that the abrasive material consists of cubic boron nitride.
 12. Tool according to one of claims 7 to 10, characterized in that the abrasive material consists of diamond.
 13. Tool according to one of claims 7 to 12, characterized in that the metal body is formed from steel.
 14. Tool according to one of claims 1 to 13, characterized in that the drive for the tool wheel (5) is designed as a hydraulic drive.
 15. Tool according to one of claims 1 to 14, characterized in that the bearing arrangement of the tool wheel (5) is designed as a hydrodynamic bearing arrangement.
 16. Tool according to one of claims 1 to 15, characterized in that the base body is designed in one piece with the holding arm (4), which accommodates supply lines (8) for the drive and/or the bearing arrangement.
 17. Tool according to one of claims 1 to 16, characterized in that holding arm (4) is provided with a tool-centering interface (11) for securing to a machine tool. 